In conventional packet, frame or cell based systems there are typically two modes of communication: point-to-point (also known as Unicast) and point-to-multipoint (also known as Multicast). Multicast addresses typically differ from Unicast addresses in that they refer to an intermediate abstraction known as a group. All senders address their transmitted information to this group and all receivers are "tuned" to "listen" to that address to receive the information transmitted to that group by the senders. The senders of information are thus effectively de-coupled from the set of receivers. Senders do not need to know who the receivers are--they simply transmit packets addressed to the group. Similarly, receivers do not need to know who the senders are--they simply send a request to the network (routers) to join a specific group of interest.
Multimedia distribution and conferencing/collaboration systems are advantageously and efficiently supported by Multicast communication methods. As will be used herein, a specific Multicast communication is referred to as a session. In the prior art, it is not possible for Unicast endpoints to access Multicast sessions, due to the differences in addressing modes and receiving modes. This disadvantageously limits the ability of a user at a Unicast endpoint client to participate in sessions in which they have interest and in which they could be an active participant.